Communication terminal apparatus

ABSTRACT

A determination section  301  determines whether or not a DSCH has been assigned to the communication terminal apparatus in question, and outputs a signal indicating the result of that determination to a transmission controller  102,  and the transmission controller  102  changes as appropriate the degree of frequency of transmission of a signal containing shared channel information according to the result of determination by the determination section  301.  That is to say, the transmission controller  102  outputs a signal containing shared channel information to a modulator  103  with a high degree of frequency when the DSCH has been assigned to that terminal, and outputs a signal containing shared channel information to the modulator  103  with a low degree of frequency when the DSCH has not been assigned to that terminal.

TECHNICAL FIELD

[0001] The present invention relates to a communication terminalapparatus, base station apparatus, and radio communication method foruse in high-speed data communication.

BACKGROUND ART

[0002] One multiple access method in a digital radio communicationsystem is CDMA (Code Division Multiple Access). In a standardestablished by 3GPP (3rd Generation Partnership Project), a standardsbody related to mobile radio communication systems, this CDMA method isused and a Downlink Shared Channel (DSCH) used for high-speed datacommunication in a downlink (a channel from a base station to acommunication terminal) is stipulated as one channel shared by aplurality of communication terminals.

[0003] As this DSCH is used by being assigned to each communicationterminal on a specified transmission unit basis (for example, on aframe-by-frame basis), its use is anticipated in downlink high-speedpacket transmission, etc.

[0004] In high-speed packet transmission using a DSCH, a base stationgenerally performs DSCH assignment to each communication terminalaccording to information indicating communication quality (such as thereceived SIR at each communication terminal, for example), informationindicating the modulation/demodulation method, and so forth, in theevent of DSCH assignment requests from communication terminals.

[0005] Also, since the above-described DSCH is assigned to communicationterminals on a per-predetermined-transmission-unit basis, in high-speedpacket transmission using a DSCH there are many cases in which packetsto a particular communication terminal are transmitted dispersedtime-wise.

[0006] A downlink channel for high-speed data communication shared by aplurality of communication terminals, as with a DSCH, is hereinafterreferred to as a “shared channel”, and information required duringassignment of this shared channel or during communication using a sharedchannel is hereinafter referred to as “shared channel information”.

[0007] However, in a conventional radio communication method, eachcommunication terminal constantly transmits shared channel informationto a base station regardless of whether or not there is a DSCHassignment request. Also, each communication terminal constantlytransmits shared channel information to a base station even when theDSCH has not been assigned to that terminal.

[0008] When communication terminals constantly transmit shared channelinformation to a base station in this way, there are problems in thatcommunication terminal power consumption increases, and in addition,interference imposed by a signal containing shared channel informationon other signals increases in uplinks (channels from communicationterminals to a base station). Moreover, the increase in interferenceresults in a problem of reduced system capacity.

DISCLOSURE OF INVENTION

[0009] It is an object of the present invention to provide acommunication terminal apparatus, base station apparatus, and radiocommunication method that enable communication terminal apparatus powerconsumption to be reduced, and also enable interference in uplinks to bereduced.

[0010] The present inventors arrived at the present invention by notingthat there is a difference in the degree of frequency and content ofshared channel information needed by a base station when a DSCH iseither assigned or not.

[0011] That is to say, the present inventors arrived at the presentinvention by noting that a communication terminal to which a DSCH isassigned needs to constantly transmit shared channel information so thata base station can keep up with changes in propagation path conditionsand changes in the modulation/demodulation method in real time andtransmit the DSCH signal efficiently, whereas a communication terminalto which a DSCH is not assigned needs to only transmit shared channelinformation at the minimum degree of frequency necessary for DSCHassignment to be performed by the base station, and finding that acommunication terminal to which the DSCH is not assigned can reduce thefrequency of transmission of shared channel information.

[0012] Furthermore, the present inventors arrived at the presentinvention by noting that a communication terminal to which a DSCH isassigned needs to transmit all shared channel information including themodulation/demodulation method, and so forth, whereas a communicationterminal to which a DSCH is not assigned needs to transmit, of sharedchannel information, only information necessary for DSCH assignment tobe performed by the base station (information indicating communicationquality, etc.), and finding that a communication terminal to which theDSCH is not assigned can reduce the amount of information in sharedchannel information.

[0013] Thus, in order to achieve the above object, the present inventionchanges as appropriate the degree of frequency of transmission andamount of information of shared channel information according tonecessity at a base station, and transmits only the necessary amount ofshared channel information according to the communication conditionsbetween a communication terminal and a base station, thereby enablingthe communication terminal power consumption to be reduced, and alsoenabling interference in uplinks to be reduced.

BRIEF DESCRIPTION OF DRAWINGS

[0014]FIG. 1 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 1 of thepresent invention;

[0015]FIG. 2 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 1 of the presentinvention;

[0016]FIG. 3 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 2 of thepresent invention;

[0017]FIG. 4 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 3 of the presentinvention; and

[0018]FIG. 5 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 3 of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] With reference now to the accompanying drawings, embodiments ofthe present invention will be explained in detail below. In thefollowing descriptions, a downlink channel for high-speed datacommunication shared by a plurality of communication terminals, as witha DSCH, is referred to as a “shared channel”, and information needed forassignment of this shared channel and communication using the sharedchannel is referred to as “shared channel information”. Shared channelinformation includes information indicating communication quality (forexample, the received SIR of a communication terminal), base stationselection information, information indicating themodulation/demodulation method according to propagation path conditions,information indicating the spreading ratio according to propagation pathconditions, a receive packet number needed for retransmission control,and so forth.

[0020] Also, in the following descriptions a case is described where aDSCH is used as a shared channel, but this is not a limitation, and thefollowing embodiments can also be implemented in a case where a channelother than a DSCH is used as a shared channel.

[0021] (Embodiment 1)

[0022] A communication terminal apparatus according to Embodiment 1 ofthe present invention changes the degree of frequency of transmission ofshared channel information as appropriate according to whether or notthere is a DSCH assignment request.

[0023]FIG. 1 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 1 of thepresent invention. In the communication terminal apparatus shown in FIG.1, when a high-speed data (for example, high-speed packet) receptionrequest is issued by a communication terminal user, a request signalgenerator 101 generates a signal (hereinafter referred to as “DSCHassignment request signal”) for requesting DSCH assignment to thatcommunication terminal apparatus by a base station apparatus. Atransmission controller 102 changes the degree of frequency oftransmission of a signal containing shared channel information.

[0024] A modulator 103 executes predetermined modulation processing onthe transmit signal, and a spreader 104 executes predetermined spreadingprocessing on the transmit signal. A transmission/reception separator105 outputs the transmit signal to an antenna 106, and outputs areceived signal to a despreader 107.

[0025] The despreader 107 executes predetermined despreading processingon the received signal, and a demodulator 108 executes predetermineddemodulation processing on the received signal. By this means, ademodulated signal is obtained.

[0026] Next, the configuration of a base station apparatus that performsradio communication with the above communication terminal apparatus willbe described. FIG. 2 is a main block diagram showing a schematicconfiguration of a base station apparatus according to Embodiment 1 ofthe present invention.

[0027] In the base station apparatus shown in FIG. 2, atransmission/reception separator 202 outputs a transmit signal to anantenna 201, and outputs a received signal to a despreader 203. Thedespreader 203 despreads the received signal with a despreading codecorresponding to an individual communication terminal. A demodulator 204executes predetermined demodulation processing on the received signal.By this means, a demodulated signal is obtained. A despreader 203 anddemodulator 204 are provided corresponding to each communicationterminal apparatus.

[0028] A DSCH-using terminal determination section 205 determines thecommunication terminal to which the DSCH is to be assigned according toshared channel information contained in the demodulated signal. A dataselector 206 selects a signal for the communication terminal apparatusto which the DSCH has been assigned from a plurality of transmitsignals.

[0029] A modulator 207 executes predetermined modulation processing onthe transmit signal. A spreader 208 spreads the transmit signal with aspreading code corresponding to an individual communication terminal. Amodulator 207 and spreader 208 are provided corresponding to eachcommunication terminal apparatus.

[0030] Next, the operation of a communication terminal apparatus andbase station apparatus with the above configurations will be described,again using FIG. 1 and FIG. 2.

[0031] In the communication terminal apparatus shown in FIG. 1, when aDSCH assignment request signal is output from the request signalgenerator 101, subsequent to output of the DSCH assignment requestsignal the transmission controller 102 outputs a signal containingshared channel information to the modulator 103 with a high degree offrequency. While a DSCH assignment request signal is not being outputfrom the request signal generator 101, the transmission controller 102outputs a signal containing shared channel information to the modulator103 with a low degree of frequency. The DSCH assignment request signalis also output from the transmission controller 102 to the modulator103.

[0032] “A low degree of frequency” here means the minimum degree offrequency of transmission necessary for DSCH assignment to be performedby the base station apparatus, and “a high degree of frequency” means adegree of frequency higher than the low degree of frequency, being adegree of frequency that enables high-speed data to be transmitted withthe base station apparatus adequately keeping up with changes in thespreading ratio and modulation method when such changes are made by acommunication terminal apparatus.

[0033] Specifically, when a DSCH assignment request signal is output,the transmission controller 102 subsequently outputs a signal containingshared channel information to the modulator 103 in each slot of a frame,for example, and while a DSCH assignment request signal is not beingoutput, the transmission controller 102 outputs a signal containingshared channel information to the modulator 103 in only one slot of aframe. That is to say, when a DSCH assignment request signal is output,the transmission controller 102 subsequently outputs a signal containingshared channel information to the modulator 103 using a short period,and while a DSCH assignment request signal is not being output, thetransmission controller 102 outputs a signal containing shared channelinformation to the modulator 103 using a longer period than the shortperiod.

[0034] The signal containing shared channel information and the DSCHassignment request signal are transmitted to the base station apparatususing a dedicated communication channel.

[0035] In the base station apparatus shown in FIG. 2, the communicationterminal to which the DSCH is to be assigned is determined by theDSCH-using terminal determination section 205 according to the signalcontaining shared channel information and the DSCH assignment requestsignal output from the demodulator 204. Then a signal indicating thecommunication terminal to which the DSCH has been assigned and a signalfor notifying the communication terminal apparatus that the DSCH hasbeen assigned are output to the data selector 206.

[0036] In the data selector 206, a signal for the communication terminalto which the DSCH has been assigned is selected from a plurality oftransmit signals according to the signal indicating the communicationterminal to which the DSCH has been assigned. The selected signal isoutput to the modulator 207, and is transmitted to the communicationterminal apparatus using the DSCH. The signal for notifying thecommunication terminal apparatus that the DSCH has been assigned isoutput to the modulator 207, and is transmitted to the communicationterminal apparatus using a dedicated communication channel.

[0037] For a signal to be transmitted using the DSCH, the DSCH-usingterminal determination section 205 changes the modulation method andspreading ratio adaptively by controlling the modulator 207 and spreader208 in accordance with shared channel information transmitted from thecommunication terminal to which the DSCH has been assigned.

[0038] Here, since a communication terminal apparatus that transmits aDSCH assignment request signal transmits shared channel information witha high degree of frequency, as described above, the base stationapparatus can transmit signals using the DSCH, adequately keeping upwith changes in the spreading ratio and modulation method by thecommunication terminal apparatus. Therefore, the base station apparatuscan adaptively change the spreading ratio and modulation method ofsignals transmitted using the DSCH in accordance with changes ofpropagation path conditions.

[0039] Thus, according to a communication terminal apparatus of thisembodiment, the degree of frequency of transmission of shared channelinformation is changed as appropriate according to whether or not thereis a DSCH assignment request, and an interval is provided in whichshared channel information is transmitted with a low degree offrequency, thereby enabling communication terminal power consumption tobe reduced, and also enabling interference in uplinks to be reduced.

[0040] (Embodiment 2)

[0041] A communication terminal apparatus according to Embodiment 2 ofthe present invention has almost the same configuration as in Embodiment1, differing in that the degree of frequency of transmission of sharedchannel information is changed as appropriate according to whether ornot there is DSCH assignment to that terminal.

[0042]FIG. 3 is a main block diagram showing a schematic configurationof a communication terminal apparatus according to Embodiment 2 of thepresent invention. Parts in FIG. 3 identical to those in Embodiment 1are assigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0043] In the communication terminal apparatus shown in FIG. 3, adetermination section 301 determines whether or not the DSCH has beenassigned to that terminal, and outputs a signal indicating the result ofthe determination to a transmission controller 102. Specifically, if asignal indicating that the DSCH has been assigned is included in thesignal output from a demodulator 108, the determination section 301determines that the DSCH has been assigned to that terminal, and if asignal indicating that the DSCH has been assigned is not included, thedetermination section 301 determines that the DSCH has not been assignedto that terminal.

[0044] The transmission controller 102 changes the degree of frequencyof transmission of a signal containing shared channel informationappropriately according to the result of the determination by thedetermination section 301. That is to say, the transmission controller102 outputs a signal containing shared channel information to themodulator 103 with a high degree of frequency when the DSCH has beenassigned to that communication terminal apparatus, and outputs a signalcontaining shared channel information to the modulator 103 with a lowdegree of frequency when the DSCH has not been assigned to thatcommunication terminal apparatus.

[0045] Thus, according to a communication terminal apparatus of thisembodiment, the degree of frequency of transmission of shared channelinformation is changed as appropriate according to whether or not thereis DSCH assignment to the terminal in question, and an interval isprovided in which shared channel information is transmitted with a lowdegree of frequency, thereby enabling communication terminal powerconsumption to be reduced, and also enabling interference in uplinks tobe reduced.

[0046] (Embodiment 3)

[0047] A communication terminal apparatus according to Embodiment 3 ofthe present invention has almost the same configuration as in Embodiment2, differing in that the degree of frequency of transmission of sharedchannel information is changed from a high degree of frequency to a lowdegree of frequency at the end of transmission of a signal transmittedto that terminal using a DSCH.

[0048]FIG. 4 is a main block diagram showing a schematic configurationof a base station apparatus according to Embodiment 3 of the presentinvention. Parts in FIG. 4 identical to those in Embodiment 1 areassigned the same codes as in Embodiment 1 and their detailedexplanations are omitted.

[0049] In the base station apparatus shown in FIG. 4, an EOT (End OfTransmission) signal multiplexer 401 detects the end of a signaltransmitted using the DSCH for each communication terminal apparatusthat is a transmission destination, and multiplexes with that end signala signal (hereinafter referred to as “EOT signal”) indicating that thisis the end of transmission. The signal with the EOT signal multiplexedis output to a modulator 207.

[0050] Next, the configuration of a communication terminal apparatusthat performs radio communication with the above-described base stationapparatus will be described. FIG. 5 is a main block diagram showing aschematic configuration of a communication terminal apparatus accordingto Embodiment 3 of the present invention.

[0051] In the communication terminal apparatus shown in FIG. 5, an EOTsignal detector 501 detects the end of a signal transmitted using theDSCH, and outputs a signal reporting detection of this signal to atransmission controller 102. Specifically, the EOT signal detector 501detects the end of a signal transmitted using the DSCH by detecting anEOT signal multiplexed with the signal output from a demodulator 108.

[0052] When transmission of a signal transmitted to that terminal usingthe DSCH ends, the transmission controller 102 reduces the degree offrequency of transmission of a signal containing shared channelinformation. Specifically, in the interval until an EOT signal isdetected, the transmission controller 102 outputs a signal containingshared channel information to a modulator 103 with a high degree offrequency, and after an EOT signal is detected, the transmissioncontroller 102 outputs a signal containing shared channel information tothe modulator 103 with a low degree of frequency.

[0053] Thus, according to a communication terminal apparatus of thisembodiment, the degree of frequency of transmission of shared channelinformation is changed from a high degree of frequency to a low degreeof frequency at the end of transmission of a signal transmitted to theterminal in question using a DSCH, and an interval is provided in whichshared channel information is transmitted at a low degree of frequency,thereby enabling communication terminal power consumption to be reduced,and also enabling interference in uplinks to be reduced.

[0054] The present invention can also be implemented by combining aboveEmbodiments 1 through 3 as appropriate. That is to say, a communicationterminal apparatus can be simultaneously provided with two or three ofthe following: a request signal generator 101, a determination section301, and an EOT signal detector 501.

[0055] Also, in above Embodiments 1 through 3, it is possible to changethe amount of shared channel information instead of changing the degreeof frequency of transmission of shared channel information.Specifically, when a DSCH assignment request occurs, when the DSCH hasbeen assigned, and when an EOT signal has not been detected, allinformation included in shared channel information (informationindicating communication quality, base station selection information,information indicating the modulation/demodulation method according topropagation path conditions, information indicating the spreading ratioaccording to propagation path conditions, a receive packet numbernecessary for retransmission control, and so forth) is transmitted,whereas when there is no DSCH assignment request, when the DSCH has notbeen assigned, and when an EOT signal is detected, of shared channelinformation, only the minimum information necessary for DSCH assignment(information indicating communication quality and base station selectioninformation) is transmitted. By providing an interval in which theamount of information is changed and the amount of information isreduced in this way, also, communication terminal power consumption canbe reduced, and interference in uplinks can also be reduced.

[0056] Furthermore, in above Embodiments 1 through 3, the example hasbeen given of a radio communication system in which downlink high-speeddata communication is performed using a DSCH, but this is not alimitation, and the present invention can be applied to any radiocommunication system in which a base station apparatus performs downlinkhigh-speed data communication by determining shared channel assignmentin accordance with shared channel information transmitted from acommunication terminal apparatus.

[0057] As described above, according to the present invention it ispossible to reduce communication terminal power consumption. Also,according to the present invention, it is possible to reduceinterference in uplinks, and also to increase system capacity.

[0058] This application is based on Japanese Patent Application No.2000-189410 filed on Jun. 23, 2000, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

[0059] The present invention is applicable to a radio communicationsystem in which a base station apparatus performs downlink high-speeddata communication by determining shared channel assignment inaccordance with shared channel information transmitted from acommunication terminal apparatus.

1. A communication terminal apparatus that provides an interval in whichshared channel information necessary for assignment of a shared channelshared by a plurality of communication terminal apparatuses and assignedon a predetermined transmission unit basis to each communicationterminal apparatus and during communication using said shared channel istransmitted at a minimum degree of frequency necessary for assignment ofsaid shared channel.
 2. A base station apparatus that performs radiocommunication with the communication terminal apparatus according toclaim 1, said base station apparatus assigning said shared channel toeach communication terminal apparatus using shared channel informationtransmitted at a minimum degree of frequency necessary for assignment ofsaid shared channel.
 3. A communication terminal apparatus that providesan interval in which shared channel information necessary for assignmentof a shared channel shared by a plurality of communication terminalapparatuses and assigned on a predetermined transmission unit basis toeach communication terminal apparatus and during communication usingsaid shared channel is transmitted with a minimum amount of informationnecessary for assignment of said shared channel.
 4. A base stationapparatus that performs radio communication with the communicationterminal apparatus according to claim 3, said base station apparatusassigning said shared channel to each communication terminal apparatususing shared channel information transmitted with a minimum amount ofinformation necessary for assignment of said shared channel.
 5. Acommunication terminal apparatus comprising: a transmitter thattransmits shared channel information necessary for assignment of ashared channel shared by a plurality of communication terminalapparatuses and assigned on a predetermined transmission unit basis toeach communication terminal apparatus and during communication usingsaid shared channel; and a controller that controls a degree offrequency of transmission of said shared channel information accordingto conditions of communication with a base station apparatus.
 6. Thecommunication terminal apparatus according to claim 5, furthercomprising a requesting circuit that requests a base station apparatusto assign said shared channel to that communication terminal apparatusitself; wherein said controller makes a degree of frequency oftransmission a predetermined degree of frequency subsequent tooccurrence of said request, and makes said degree of frequency oftransmission a degree of frequency lower than said predetermined degreeof frequency in an interval until said request occurs.
 7. Thecommunication terminal apparatus according to claim 5, furthercomprising a determination circuit that determines whether or not saidshared channel has been assigned to that communication terminalapparatus itself; wherein said controller makes a degree of frequency oftransmission a predetermined degree of frequency when said sharedchannel has been assigned, and makes said degree of frequency oftransmission a degree of frequency lower than said predetermined degreeof frequency when said shared channel has not been assigned.
 8. Thecommunication terminal apparatus according to claim 5, furthercomprising a detector that detects an end of data transmitted to thatcommunication terminal apparatus itself using said shared channel;wherein said controller makes a degree of frequency of transmission apredetermined degree of frequency while said data is being transmitted,and makes said degree of frequency of transmission a degree of frequencylower than said predetermined degree of frequency subsequent todetection of said end of data.
 9. A base station apparatus that performsradio communication with the communication terminal apparatus accordingto claim 8, said base station apparatus comprising: a detector thatdetects for each communication terminal apparatus an end of datatransmitted using said shared channel; and a reporting circuit thatreports said end of data to said each communication terminal apparatus.10. A communication terminal apparatus comprising: a transmitter thattransmits shared channel information necessary for assignment of ashared channel shared by a plurality of communication terminalapparatuses and assigned on a predetermined transmission unit basis toeach communication terminal apparatus and during communication usingsaid shared channel; and a controller that controls an amount ofinformation of said shared channel information according to conditionsof communication with a base station apparatus.
 11. The communicationterminal apparatus according to claim 10, further comprising arequesting circuit that requests a base station apparatus to assign saidshared channel to that communication terminal apparatus itself; whereinsaid controller includes in said shared channel information allinformation necessary during communication using said shared channelsubsequent to occurrence of said request, and includes in said sharedchannel information only information necessary for assignment of saidshared channel in an interval until said request occurs.
 12. Thecommunication terminal apparatus according to claim 10, furthercomprising a determination circuit that determines whether or not saidshared channel has been assigned to that communication terminalapparatus itself; wherein said controller includes in said sharedchannel information all information necessary during communication usingsaid shared channel when said shared channel has been assigned, andincludes in said shared channel information only information necessaryfor assignment of said shared channel when said shared channel has notbeen assigned.
 13. The communication terminal apparatus according toclaim 10, further comprising a detector that detects an end of datatransmitted to that communication terminal apparatus itself using saidshared channel; wherein said controller includes in said shared channelinformation all information necessary during communication using saidshared channel while said data is being transmitted, and includes insaid shared channel information only information necessary forassignment of said shared channel subsequent to detection of said end ofdata.
 14. A base station apparatus that performs radio communicationwith the communication terminal apparatus according to claim 13, saidbase station apparatus comprising: a detector that detects for eachcommunication terminal apparatus an end of data transmitted using saidshared channel; and a reporting circuit that reports said end of data tosaid each communication terminal apparatus.
 15. A radio communicationmethod that provides an interval in which shared channel informationnecessary for assignment of a shared channel shared by a plurality ofcommunication terminal apparatuses and assigned on a predeterminedtransmission unit basis to each communication terminal apparatus andduring communication using said shared channel is transmitted at aminimum degree of frequency necessary for assignment of said sharedchannel.
 16. A radio communication method that provides an interval inwhich shared channel information necessary for assignment of a sharedchannel shared by a plurality of communication terminal apparatuses andassigned on a predetermined transmission unit basis to eachcommunication terminal apparatus and during communication using saidshared channel is transmitted with a minimum amount of informationnecessary for assignment of said shared channel.
 17. A radiocommunication method comprising: a transmitting step of transmittingshared channel information necessary for assignment of a shared channelshared by a plurality of communication terminal apparatuses and assignedon a predetermined transmission unit basis to each communicationterminal apparatus and during communication using said shared channel;and a controlling step of controlling a degree of frequency oftransmission of said shared channel information according to conditionsof communication with a base station apparatus.
 18. A radiocommunication method comprising: a transmitting step of transmittingshared channel information necessary for assignment of a shared channelshared by a plurality of communication terminal apparatuses and assignedon a predetermined transmission unit basis to each communicationterminal apparatus and during communication using said shared channel;and a controlling step of controlling an amount of information of saidshared channel information according to conditions of communication witha base station apparatus.